ext4: remove metadata reservation checks

Commit 27dd4385 ("ext4: introduce reserved space") reserves 2% of
the file system space to make sure metadata allocations will always
succeed.  Given that, tracking the reservation of metadata blocks is
no longer necessary.
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/balloc.c

@@ -639,7 +639,6 @@ ext4_fsblk_t ext4_new_meta_blocks(handle_t *handle, struct inode *inode,
 	if (!(*errp) &&
 	    ext4_test_inode_state(inode, EXT4_STATE_DELALLOC_RESERVED)) {
 		spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
-		EXT4_I(inode)->i_allocated_meta_blocks += ar.len;
 		spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
 		dquot_alloc_block_nofail(inode,
 				EXT4_C2B(EXT4_SB(inode->i_sb), ar.len));

fs/ext4/ext4.h

@@ -591,7 +591,6 @@ enum {
 #define EXT4_FREE_BLOCKS_NO_QUOT_UPDATE	0x0008
 #define EXT4_FREE_BLOCKS_NOFREE_FIRST_CLUSTER	0x0010
 #define EXT4_FREE_BLOCKS_NOFREE_LAST_CLUSTER	0x0020
-#define EXT4_FREE_BLOCKS_RESERVE		0x0040
 
 /*
  * ioctl commands

fs/ext4/extents.c

@@ -1808,8 +1808,7 @@ static void ext4_ext_try_to_merge_up(handle_t *handle,
 
 	brelse(path[1].p_bh);
 	ext4_free_blocks(handle, inode, NULL, blk, 1,
-			 EXT4_FREE_BLOCKS_METADATA | EXT4_FREE_BLOCKS_FORGET |
-			 EXT4_FREE_BLOCKS_RESERVE);
+			 EXT4_FREE_BLOCKS_METADATA | EXT4_FREE_BLOCKS_FORGET);
 }
 
 /*

fs/ext4/inode.c

@@ -324,18 +324,6 @@ qsize_t *ext4_get_reserved_space(struct inode *inode)
 }
 #endif
 
-/*
- * Calculate the number of metadata blocks need to reserve
- * to allocate a block located at @lblock
- */
-static int ext4_calc_metadata_amount(struct inode *inode, ext4_lblk_t lblock)
-{
-	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
-		return ext4_ext_calc_metadata_amount(inode, lblock);
-
-	return ext4_ind_calc_metadata_amount(inode, lblock);
-}
-
 /*
  * Called with i_data_sem down, which is important since we can call
  * ext4_discard_preallocations() from here.
@@ -357,35 +345,10 @@ void ext4_da_update_reserve_space(struct inode *inode,
 		used = ei->i_reserved_data_blocks;
 	}
 
-	if (unlikely(ei->i_allocated_meta_blocks > ei->i_reserved_meta_blocks)) {
-		ext4_warning(inode->i_sb, "ino %lu, allocated %d "
-			"with only %d reserved metadata blocks "
-			"(releasing %d blocks with reserved %d data blocks)",
-			inode->i_ino, ei->i_allocated_meta_blocks,
-			     ei->i_reserved_meta_blocks, used,
-			     ei->i_reserved_data_blocks);
-		WARN_ON(1);
-		ei->i_allocated_meta_blocks = ei->i_reserved_meta_blocks;
-	}
-
 	/* Update per-inode reservations */
 	ei->i_reserved_data_blocks -= used;
-	ei->i_reserved_meta_blocks -= ei->i_allocated_meta_blocks;
-	percpu_counter_sub(&sbi->s_dirtyclusters_counter,
-			   used + ei->i_allocated_meta_blocks);
-	ei->i_allocated_meta_blocks = 0;
+	percpu_counter_sub(&sbi->s_dirtyclusters_counter, used);
 
-	if (ei->i_reserved_data_blocks == 0) {
-		/*
-		 * We can release all of the reserved metadata blocks
-		 * only when we have written all of the delayed
-		 * allocation blocks.
-		 */
-		percpu_counter_sub(&sbi->s_dirtyclusters_counter,
-				   ei->i_reserved_meta_blocks);
-		ei->i_reserved_meta_blocks = 0;
-		ei->i_da_metadata_calc_len = 0;
-	}
 	spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
 
 	/* Update quota subsystem for data blocks */
@@ -1221,49 +1184,6 @@ static int ext4_journalled_write_end(struct file *file,
 	return ret ? ret : copied;
 }
 
-/*
- * Reserve a metadata for a single block located at lblock
- */
-static int ext4_da_reserve_metadata(struct inode *inode, ext4_lblk_t lblock)
-{
-	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
-	struct ext4_inode_info *ei = EXT4_I(inode);
-	unsigned int md_needed;
-	ext4_lblk_t save_last_lblock;
-	int save_len;
-
-	/*
-	 * recalculate the amount of metadata blocks to reserve
-	 * in order to allocate nrblocks
-	 * worse case is one extent per block
-	 */
-	spin_lock(&ei->i_block_reservation_lock);
-	/*
-	 * ext4_calc_metadata_amount() has side effects, which we have
-	 * to be prepared undo if we fail to claim space.
-	 */
-	save_len = ei->i_da_metadata_calc_len;
-	save_last_lblock = ei->i_da_metadata_calc_last_lblock;
-	md_needed = EXT4_NUM_B2C(sbi,
-				 ext4_calc_metadata_amount(inode, lblock));
-	trace_ext4_da_reserve_space(inode, md_needed);
-
-	/*
-	 * We do still charge estimated metadata to the sb though;
-	 * we cannot afford to run out of free blocks.
-	 */
-	if (ext4_claim_free_clusters(sbi, md_needed, 0)) {
-		ei->i_da_metadata_calc_len = save_len;
-		ei->i_da_metadata_calc_last_lblock = save_last_lblock;
-		spin_unlock(&ei->i_block_reservation_lock);
-		return -ENOSPC;
-	}
-	ei->i_reserved_meta_blocks += md_needed;
-	spin_unlock(&ei->i_block_reservation_lock);
-
-	return 0;       /* success */
-}
-
 /*
  * Reserve a single cluster located at lblock
  */
@@ -1273,8 +1193,6 @@ static int ext4_da_reserve_space(struct inode *inode, ext4_lblk_t lblock)
 	struct ext4_inode_info *ei = EXT4_I(inode);
 	unsigned int md_needed;
 	int ret;
-	ext4_lblk_t save_last_lblock;
-	int save_len;
 
 	/*
 	 * We will charge metadata quota at writeout time; this saves
@@ -1295,25 +1213,15 @@ static int ext4_da_reserve_space(struct inode *inode, ext4_lblk_t lblock)
 	 * ext4_calc_metadata_amount() has side effects, which we have
 	 * to be prepared undo if we fail to claim space.
 	 */
-	save_len = ei->i_da_metadata_calc_len;
-	save_last_lblock = ei->i_da_metadata_calc_last_lblock;
-	md_needed = EXT4_NUM_B2C(sbi,
-				 ext4_calc_metadata_amount(inode, lblock));
-	trace_ext4_da_reserve_space(inode, md_needed);
+	md_needed = 0;
+	trace_ext4_da_reserve_space(inode, 0);
 
-	/*
-	 * We do still charge estimated metadata to the sb though;
-	 * we cannot afford to run out of free blocks.
-	 */
-	if (ext4_claim_free_clusters(sbi, md_needed + 1, 0)) {
-		ei->i_da_metadata_calc_len = save_len;
-		ei->i_da_metadata_calc_last_lblock = save_last_lblock;
+	if (ext4_claim_free_clusters(sbi, 1, 0)) {
 		spin_unlock(&ei->i_block_reservation_lock);
 		dquot_release_reservation_block(inode, EXT4_C2B(sbi, 1));
 		return -ENOSPC;
 	}
 	ei->i_reserved_data_blocks++;
-	ei->i_reserved_meta_blocks += md_needed;
 	spin_unlock(&ei->i_block_reservation_lock);
 
 	return 0;       /* success */
@@ -1346,20 +1254,6 @@ static void ext4_da_release_space(struct inode *inode, int to_free)
 	}
 	ei->i_reserved_data_blocks -= to_free;
 
-	if (ei->i_reserved_data_blocks == 0) {
-		/*
-		 * We can release all of the reserved metadata blocks
-		 * only when we have written all of the delayed
-		 * allocation blocks.
-		 * Note that in case of bigalloc, i_reserved_meta_blocks,
-		 * i_reserved_data_blocks, etc. refer to number of clusters.
-		 */
-		percpu_counter_sub(&sbi->s_dirtyclusters_counter,
-				   ei->i_reserved_meta_blocks);
-		ei->i_reserved_meta_blocks = 0;
-		ei->i_da_metadata_calc_len = 0;
-	}
-
 	/* update fs dirty data blocks counter */
 	percpu_counter_sub(&sbi->s_dirtyclusters_counter, to_free);
 
@@ -1500,10 +1394,6 @@ static void ext4_print_free_blocks(struct inode *inode)
 	ext4_msg(sb, KERN_CRIT, "Block reservation details");
 	ext4_msg(sb, KERN_CRIT, "i_reserved_data_blocks=%u",
 		 ei->i_reserved_data_blocks);
-	ext4_msg(sb, KERN_CRIT, "i_reserved_meta_blocks=%u",
-	       ei->i_reserved_meta_blocks);
-	ext4_msg(sb, KERN_CRIT, "i_allocated_meta_blocks=%u",
-	       ei->i_allocated_meta_blocks);
 	return;
 }
 
@@ -1620,13 +1510,6 @@ static int ext4_da_map_blocks(struct inode *inode, sector_t iblock,
 				retval = ret;
 				goto out_unlock;
 			}
-		} else {
-			ret = ext4_da_reserve_metadata(inode, iblock);
-			if (ret) {
-				/* not enough space to reserve */
-				retval = ret;
-				goto out_unlock;
-			}
 		}
 
 		ret = ext4_es_insert_extent(inode, map->m_lblk, map->m_len,
@@ -2843,8 +2726,7 @@ int ext4_alloc_da_blocks(struct inode *inode)
 {
 	trace_ext4_alloc_da_blocks(inode);
 
-	if (!EXT4_I(inode)->i_reserved_data_blocks &&
-	    !EXT4_I(inode)->i_reserved_meta_blocks)
+	if (!EXT4_I(inode)->i_reserved_data_blocks)
 		return 0;
 
 	/*

fs/ext4/mballoc.c

@@ -4627,7 +4627,6 @@ void ext4_free_blocks(handle_t *handle, struct inode *inode,
 	struct buffer_head *gd_bh;
 	ext4_group_t block_group;
 	struct ext4_sb_info *sbi;
-	struct ext4_inode_info *ei = EXT4_I(inode);
 	struct ext4_buddy e4b;
 	unsigned int count_clusters;
 	int err = 0;
@@ -4838,19 +4837,7 @@ void ext4_free_blocks(handle_t *handle, struct inode *inode,
 			     &sbi->s_flex_groups[flex_group].free_clusters);
 	}
 
-	if (flags & EXT4_FREE_BLOCKS_RESERVE && ei->i_reserved_data_blocks) {
-		percpu_counter_add(&sbi->s_dirtyclusters_counter,
-				   count_clusters);
-		spin_lock(&ei->i_block_reservation_lock);
-		if (flags & EXT4_FREE_BLOCKS_METADATA)
-			ei->i_reserved_meta_blocks += count_clusters;
-		else
-			ei->i_reserved_data_blocks += count_clusters;
-		spin_unlock(&ei->i_block_reservation_lock);
-		if (!(flags & EXT4_FREE_BLOCKS_NO_QUOT_UPDATE))
-			dquot_reclaim_block(inode,
-					EXT4_C2B(sbi, count_clusters));
-	} else if (!(flags & EXT4_FREE_BLOCKS_NO_QUOT_UPDATE))
+	if (!(flags & EXT4_FREE_BLOCKS_NO_QUOT_UPDATE))
 		dquot_free_block(inode, EXT4_C2B(sbi, count_clusters));
 	percpu_counter_add(&sbi->s_freeclusters_counter, count_clusters);